1. Lecture 9. Material Balance for Processes Involving Reaction

2. 9.1 Species Material Balance

3. 9.1.1 Processes involving a single reaction

4. Examples Lecture 9.1.1 (E10.1, DMH) Reaction in which the fraction conversion is specified. The chlorination of methane occurs by the following reaction CH 4 + Cl 2 -> CH 3 Cl + HCl You are asked to determine the product composition if the conversion of the limiting reactant is 67%, and the feed composition in mole% is given as : 40% CH 4, 50% Cl 2 and 10% N 2.

5. Examples Lecture 9.1.1 (E10.2, DMH) Reaction in which the fraction conversion is to be calculated. Mercaptans, hydrogen sulfide, and other sulfur compounds are removed from natural gas by various so-called “sweeting processes” that make available other-wise useless “sour” gas. As you know H 2 S is toxic in very small quantities and is quite corrosive to process equipment. A proposed process to remove H 2 S is by reaction with SO 2 : 2 H 2 S (g) + SO 2(g) -> 3 S (s) + 2 H 2 O (g) In a test of the process, a gas stream containing 20% H 2 S and 80% CH 4 was combined with a stream of pure SO 2. The process produced 5000 lb of S (s), and in the product gas the ratio of SO 2 to H 2 S was equal to 3, and the ratio of H 2 O to H 2 S was 10. You are asked to determine the fractional conversion of the limiting reactant, and the feed rate of the H 2 S and SO 2 streams.

6. Note

7. 9.1.2 Processes involving a multiple reaction

8. Examples Lecture 9.1.2 (E10.3, DMH) Material balances for a process in which two simultaneous reactions occur Formaldehyde (CH 2 O) is produced industrially by the catalytic oxidation of methanol (CH 3 OH) according to the following reaction: CH 3 OH +1/2 O 2 -> CH 2 O + H 2 O(1) Unfortunately, under the conditions used to produce formaldehyde at a profitable rate, a significant portion of the formaldehyde reacts with oxygen to produce CO and H 2 O, that is, CH 2 O + ½ O 2 -> CO + H 2 O(2) Assume that methanol and twice the stoichiometric amount of air needed for complete conversion of the CH 3 OH to the desired products (CH 2 O and H 2 O) are fed to the reactor. Also assume that 90% conversion of the methanol results, and that 75% yield of formaldehyde occurs based on the theoretical production of CH 2 O by Reaction (1). Determine the composition of the product gas leaving the reactor.

9. Examples Lecture 9.1.2 (E10.4, DMH) Material balances for a process in which two simultaneous reactions occur A bioreactor is a vessel in which biological conversion is carred out involving enzymes, microorganisms, and/or animal and plant cells. In the anaerobic fermentation of grain, the yeast Saccharomyces cerevisiae digests glucose (C 6 H 12 O 6 ) from plants to form the products ethanol (C 2 H 5 OH) and propenoic acid (C 2 H 3 CO 2 H) by the following overall reactions: Reaction 1 :C 6 H 12 O 6 -> 2 C 2 H 5 OH + 2 CO 2 Reaction 2 :C 6 H 12 O 6 -> 2 C 2 H 3 CO 2 H + 2 H 2 O In a batch process, a tank is charged with 4000 kg of a 12% solution of glucose in water. After fermentation, 120 kg of CO 2 are produced and 90 kg of unreacted glucose remains in the broth. What are the weight (mass) percents of ethanol and propenic acid in the broth at the end of the fermentation process? Assume that none of the glucose is assimilated into the bacteria.

10. Notes